Organic flame retardants are mainly classified into three categories based on their chemical structure and application characteristics: brominated, organophosphorus, and nitrogen-based.
(I) Brominated Flame Retardants: Former "Dominators," Now "Controversial"
Brominated flame retardants dominated the market for decades due to their high flame retardant efficiency and cost-effectiveness. Currently, some varieties face bans or restrictions due to environmental issues, and the industry is developing towards larger molecular weights and higher stability.
Decabromodiphenyl ethane (DBDPE): An ideal substitute for decabromodiphenyl ether, as it does not produce dioxins.
Decabromodiphenyl ether (DBDPO): A traditional mainstay variety, but banned in many countries due to environmental issues.
Tetrabromobisphenol A (TBBPA): Can be used as an additive flame retardant or as a reactive monomer in the synthesis of brominated epoxy resins or flame-retardant polycarbonates.
Brominated polystyrene (BPS): A high-molecular-weight flame retardant with high thermal stability, suitable for engineering plastics such as nylon and PBT.
Tribromophenol and its derivatives: reactive intermediates used in the end-capping of brominated epoxy resins and the synthesis of brominated triazine, etc.
Brominated triazine (TTBPC): a bromine-nitrogen synergistic system with thermal stability exceeding 330℃, suitable for materials with high processing temperatures such as ABS and HIPS.
Brominated epoxy resin (BEO): divided into EP type and EC type, used in copper-clad laminates and engineering plastics, respectively.
Hexabromocyclododecane (HBCD): once widely used in EPS/XPS insulation boards, now banned; China discontinued its use at the end of 2021.
Octabromoether and methyl octabromoether: Octabromoether is used in PP/PE; methyl octabromoether, as a substitute for HBCD, is used in XPS insulation boards.
Brominated SBS: a high-molecular-weight flame retardant with good compatibility with polystyrene, a new alternative to HBCD.
Tetrabromobisphenol A polycarbonate oligomers (BC-52/BC-58): macromolecular flame retardants with excellent thermal stability.
Declone (DCRP): A chlorine-based flame retardant, its use is restricted due to its persistent organic pollutant properties.
(II) Organophosphorus Flame Retardants: The Main Force in Halogen-Free Flame Retardants
Organophosphorus flame retardants can function simultaneously in the gas phase (quenched by PO· free radicals) and the condensed phase (promoting char formation), representing an important direction for replacing bromine-based flame retardants.
Phosphate Esters: Mainly include TPP, BDP, RDP, TCPP, TCEP, etc. BDP and RDP are used in engineering plastics such as PC/ABS and PPO/HIPS; TCPP and TCEP are used in polyurethane foams.
DOPO and its Derivatives: DOPO can react with various compounds through P-H bonds, achieving inherent flame retardancy when introduced into epoxy resins, polyesters, and other matrices. Derivatives include ODOPB and TAD, which have wide applications.
Alkyl phosphonates (e.g., aluminum diethyl phosphonate, ADP): Extremely high thermal stability (>400℃), suitable for nylon and polyester, with even better synergistic effects when combined with melamine polyphosphate (MPP).
Cage-like phosphate esters (PEPA, Trimer): Single-component intumescent flame retardants with high thermal stability and good charring properties.
Phosphohydrazones(hexaphenoxycyclotriphosphohydrazone,HPCTP):Phosphorus-nitrogen heterocyclic structure, high thermal stability, used in epoxy resins, PC/ABS, etc.
(III) Nitrogen-based flame retardants: Environmentally friendly and low-toxicity "fresh and clean" Nitrogen-based flame retardants mainly exert their flame-retardant effect through sublimation endothermic reaction and dilution of flammable gases, characterized by being environmentally friendly and low-toxicity.
Melamine cyanurate (MCA): Mainly used in PA6 and PBT, exerting its flame-retardant effect through sublimation endothermic reaction and gas dilution, while also having anti-dripping properties.
Melamine phosphate (MP): Possesses both phosphorus and nitrogen synergistic effects, and can be used in polyolefins, coatings, etc.
Charring agents (triazine, piperazine): These are compounded with ammonium polyphosphate (APP) to form an intumescent flame retardant system, such as triazine charring agents and piperazine pyrophosphate.
